Wire grid polarizers may be used for polarizing light, by allowing one polarization to pass through the polarizer, and reflecting or absorbing the opposite polarization. For simplicity, the polarization that primarily passes through will be referred to as p-polarized light and the polarization that primarily reflects or absorbs will be referred to as s-polarized light. For some applications, absorption of s-polarized light is preferred, such as for example if the refection can disrupt the image or other intended use. In a transmissive panel system, reflected light may go back into the LCD Imager causing damage or image degradation, or stray light can reach the screen, degrading contrast. An ideal selectively absorptive wire grid polarizer will transmit all p-polarized light and selectively absorb all s-polarized light. In reality, some s-polarized light is transmitted and some reflected; some p-polarized light is absorbed and some reflected.
The effectiveness of a selectively absorptive wire grid polarizer can be quantified by high transmission of p-polarized light, high absorption of s-polarized light, and high contrast. Contrast is equal to a percent of p-polarized light transmitted (Tp) divided by a percent of s-polarized light transmitted (Ts): Contrast=Tp/Ts.
It can be important in wire grid polarizers for infrared, visible, and ultraviolet light to have small wires with small pitch, such as nanometer or micrometer size and pitch, for effective polarization. Typically, a pitch of less than half of the wavelength of light to be polarized is needed for effective polarization. Smaller pitches may improve the contrast. Thus, small pitch can be an important feature of wire grid polarizers. Manufacture of wire grid polarizers with sufficiently small pitch is challenging, and is a goal of research in this field.
Small wires can be damaged by handling and by environmental conditions. Protection of the wires can be important in wire grid polarizers. Durability of wire grid polarizers is thus another important feature.
For example, see U.S. Pat. Nos. 5,991,075, 6,288,840, 6,665,119, 7,630,133, 7,692,860, 7,800,823, 7,961,393, and 8,426,121; U.S. Patent Publication Numbers US 2008/0055723, US 2009/0041971, and US 2009/0053655; U.S. patent application Ser. No. 13/326,566, filed on Dec. 15, 2011; “Application of 100 Å linewidth structures fabricated by shadowing techniques” by D. C Flanders in J. Vac. Sci. Technol., 19(4), November/December 1981; and “Submicron periodicity gratings as artificial anisotropic dielectrics” by Dale C. Flanders in Appl. Phys. Lett. 42 (6), 15 Mar. 1983, pp. 492-494.